How Digital Cameras Work – FEATURES
by Karim Nice and Gerald Jay Gurevich
http://www.howstuffworks.com/digital-camera.htm?printable=1

If you are looking for a digital camera, there are a bunch of different features you need to know about so that you can pick the perfect camera for you. By learning about all of the different features you will be able to have intelligent conversations with sales people and friends, and you will also be able to decode all of the jargon you see in catalogs and store displays! Here are the most important features you need to think about when choosing a digital camera:

*      Resolution

*      Sensor Technology

*      Storage

*      Compression Formats

*      LCD

*      View Finder

*      Lens

*      Interface

*      Exposure Control

*      Image Stabilization

*      Focus

*      Macro

*      Movies

*      Batteries

*      Flash

*      Software

 

Resolution
The amount of detail that the camera can capture is called the resolution, and it is measured in pixels. In general, the more pixels your camera has, the more detail it can capture. The more detail you have, the more you can blow up a picture before it becomes "grainy," and starts to look out-of-focus. Some typical resolutions that you find in digital cameras today include:

*      256 x 256 pixels - You find this resolution on cheap cameras, like those you would buy for a child. This resolution is so low that the picture quality is almost always unacceptable. This is 65,000 total pixels.

*      640 x 480 pixels - This is the low end on most "real" cameras. This resolution is great if you plan to e-mail most of your pictures to friends or post them on a Web site. This is 307,000 total pixels.

*      1216 x 912 pixels - If you are planning to print your images, and want them to look nice, this is a good resolution. This is a "megapixel" image size -- 1,109,000 total pixels.

*      1600 x 1200 pixels - This is "high resolution." Images taken with this resolution can be printed in larger sizes, like 8 x 10 inches, with good results. This is almost 2 million total pixels. You can find cameras today with up to 3 million pixels.

You may or may not need lots of resolution, depending on what you want to do with your pictures. If you are planning to do nothing more than display images on a Web page or send them in e-mail, then using 640 x 480 resolution has several advantages:

*      Your camera's memory will hold more images at this low resolution than at higher resolutions.

*      It will take less time to move the images from the camera to your computer.

*      The images will take up less space on your computer.

On the other hand, if your goal is to print large images, you definitely want to take high resolution shots, and need a camera with lots of pixels.

 

Sensor Technology
There are two different sensors used on cameras today:

*      CCD sensors - CCD sensors have been around longer. In general, CCDs have more pixels and work better in low light. However, they tend to be more expensive and they use a lot of power.

*      CMOS sensors - CMOS sensors are lower resolution, use less power and do not work well in low light. If you are looking for an inexpensive, low-resolution camera, and plan to use it outdoors, a CMOS sensor would be a good choice.

High-resolution cameras need a CCD sensor.

 

Storage
Your camera needs to store its images somewhere, and it uses memory to do that. There are a number of storage systems currently used in digital cameras:

*      Built-in memory - Some extremely inexpensive cameras have built-in flash memory. There is no way for you to change or upgrade the memory. The built-in memory might be able to hold six to 12 images; then you must either download the images to your computer or erase images before you can take more.

*      SmartMedia cards - SmartMedia cards are small flash memory modules. The camera will come with one, and then you can purchase additional cards if you want more memory. Cards come in 4, 8, 16, 32 and 64 megabyte (MB) sizes.

*      Compact flash - Compact flash cards are another form of flash memory, similar to but slightly larger than SmartMedia cards. Capacities range up to 128 MB.

*      Memory Stick - Memory Stick is a proprietary form of flash memory used by Sony.

*      Floppy disk - Some cameras store images directly onto floppy disks. This makes image transfers easy because you can just pop a diskette out of the camera and into any computer. The problem is that a floppy disk only holds 1.4 MB of information, which is not much when you're taking high-resolution images. You can fit about 30 640 x 480 pixel images on a floppy disk.

*      Hard disk - Some higher-end cameras use small built-in hard disks, or PCMCIA hard disk cards, for image storage. Sizes can range up to a gigabyte (GB), depending on the form factor.

*      Writeable CD and DVD - some of the newest cameras are using writeable CD and DVD drives to store images. A writeable CD can hold 650 MB; a writeable DVD can hold 5.6 gigabytes (GB).

 

To choose between all of these different options, here are some things to consider:

*       If you are the sort of person who wants to take a dozen 640 x 480 snapshots at a birthday party and then upload them to your computer to e-mail them, any of these systems will do. You don't need much memory, so a floppy disk is fine, or a small amount (2 or 4 MB) of flash memory works great.

*      If you are a person who plans to go on a trip, take hundreds of pictures and then come home to look at them all, you need lots of storage space. You can do that by purchasing extra flash memory cards or by using a camera with a hard disk.

*      If you want to take high-resolution images (for example, 2 megapixel images), you need lots of storage. Purchase extra flash memory cards or use a camera with a hard disk.

 

Compression Formats
Most of today's cameras store their images in JPEG format; and you might be able to select between "fine detail mode" and "normal mode." Higher-end cameras may also support the TIFF format. While JPEG compresses the image, TIFF does not, so TIFF images take lots of space. The advantage of TIFF storage is that no data is lost to the compression process.

 

LCD
Many digital cameras come with an LCD. The LCD is often used as a viewfinder. It also allows you to review images in memory. You can then delete images that you don't like, and take more pictures in their place. Some newer cameras have advanced features for the LCD. For example, you can zoom in on parts of the image and see them in greater detail. Check to see how the LCD looks both in darkness (it needs a backlight to work in the dark) and bright sunlight.

 

View Finder
Some cameras have no LCD panel, and instead use a simple optical viewfinder. Other cameras have both an LCD panel and an optical viewfinder, in which case you can turn off the LCD to save the battery. Some cameras have only an LCD panel, which also acts as the viewfinder.

 

Lens
You will find four different types of lenses on digital cameras:

*      Fixed-focus, fixed zoom lenses - These are the kinds of lenses you find on disposable and inexpensive film cameras -- inexpensive and great for snapshots, but fairly limited.

*      Optical zoom lenses with automatic focus - similar to the lens on a video camcorder, you have "wide" and "telephoto" options and automatic focus. The camera may or may not let you switch to manual focus.

*      Digital zoom lenses - With digital zoom, the camera takes pixels from the center of the image sensor and "interpolates" them to make a full-size image. Depending on the resolution of the image and the sensor, this approach may create a grainy or fuzzy image. It turns out that you can do the same thing a digital zoom is doing on your own -- simply snap a picture and then cut out the center of the image in your image processing software.

*      Replaceable lens systems - If you are familiar with high-end 35 mm cameras, then you are familiar with the concept of replaceable lenses. High-end digital cameras can use this same system, and in fact can use lenses from 35 mm cameras in some cases.

 

Interface
The interface allows you to connect the camera to your computer and transfer the images. Once the images are on your computer, you can edit them, e-mail them, load them onto a Web site or print them out. There are at least four different ways to move images from the camera to the computer:

*      USB connection - A USB connection is a fast, easy way to download images. It works only on computers that have a USB port.

*      Serial connection - This is a slow way to download images, but works on almost any computer. You often have to load special software onto the computer to download the images.

*      Floppy disk - If your camera uses a floppy disk (or writeable CD/DVD), then you can simply pop the floppy disk into any computer.

*      Flash memory slots - It is possible to add a box to your computer that will let you remove a SmartMedia card or Compact Flash card from the camera and attach it directly to the computer.

 

Exposure Control
Most cameras have completely automatic exposure. If you want exposure control, look for a manual exposure feature. Some cameras also offer special exposure settings for specific situations like sports, indoor arenas, etc.

 

Image Stabilization
Some cameras offer a "steady cam" image stabilization system like video cameras have. A system like this can help you take clearer images.

 

Focus
Most cameras have fixed focus, so you can not adjust the focus at all, or automatic focus. If you would like more control, choose a camera with a manual focus feature.

 

Macro
If you plan to take close-up images, look for a camera that has a macro focusing capability. This feature lets you move the camera's lens very close to the subject (for example a flower or an insect).

 

Movies
Some cameras now offer an "MPEG movie" feature, allowing you to take short movies with your camera. If this is a feature that you want, make sure the camera offers it because this is not a standard feature. Look for the ability to change the resolution of the movie, and find out the maximum movie length you can record.

 

Batteries
Digital cameras, especially those that use a CCD sensor and an LCD display, tend to use lots of power -- which means they eat batteries. Rechargeable batteries help to lower the cost of using the digital camera, but rechargeable batteries are sometimes expensive. Here are some things to consider:

*      Does the camera use standard size rechargeable batteries (e.g., AA), or does it use special rechargeable batteries made by the manufacturer? If it uses the special ones, check to see what the price of another battery pack is.

*      If the camera takes AA batteries, can you use normal alkaline batteries in a pinch?

*      Are the rechargeable batteries removable, or are they permanently mounted in the camera? If they are not removable, it means, once the batteries go dead, you can't use the camera again until you can get to a recharger and power supply. This can be a major pain in the neck if you want to take a lot of pictures at once (e.g., on a vacation).

 

Flash
Most cameras come with a built-in flash. Normal modes are:

*      Automatic

*      Forced flash

*      Fill flash

*      No flash

You definitely want to be able to turn off the flash -- some completely automatic cameras do not allow this.

 

Software
Most cameras come with some sort of software. You use the software to download images from the camera and manipulate them on the computer. Unless you already have software that you are comfortable with, you want to make sure that your camera comes with something.